Variable scope and lifetime: Correct Solution

Given the following code:

public class Dontsu {
    public void banai(int pe) {
        A
        int lipe = 0;
        dul += pe;
        lipe += pe;
        po += pe;
        System.out.println("dul=" + dul + "  lipe=" + lipe + "  po=" + po);
    }

    private int po = 0;

    public static void main(String[] args) {
        Dontsu d0 = new Dontsu();
        B
        Dontsu d1 = new Dontsu();
        C
        d0.banai(1);
        d1.banai(10);
        d1 = new Dontsu();
        d0 = new Dontsu();
        d0.banai(100);
        d1.banai(1000);
    }

    private static int dul = 0;
}
  1. What does the main method print?
  2. Which of the variables [po, dul, lipe, d0, d1] are in scope at A ?
  3. Which are in scope at B ?
  4. Which are in scope at C ?

Solution

  1. Output:

    po=1  dul=1  lipe=1
po=11  dul=10  lipe=10
po=111  dul=100  lipe=100
po=1111  dul=1000  lipe=1000

  2. In scope at A : po, lipe, dul

  3. In scope at B : po, d0, d1

  4. In scope at C : po, d0, d1

Explanation (which you do not need to write out in your submitted solution):

  1. po is a static variable, lipe is an instance variable, and dul is a local variable.

  2. At A , d0 and d1 out of scope because they are local to the main method.

  3. At B , lipe is out of scope because it is an instance variable, but main is a static method. dul is out of scope because it is local to banai.

  4. At C , lipe is out of scope because it is an instance variable, but main is a static method. dul is out of scope because it is local to banai.

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